1. Field of the Invention
The present invention relates to a substrate treatment apparatus for forming electronic devices such as a thin film solar battery, particularly to a substrate treatment apparatus characterized in that a gas inlet is provided at a connection tube between a treatment chamber and a buffer chamber.
2. Description of the Related Art
Recently, in view of mass production of thin film solar batteries, a low-cost manufacture process for the thin film solar battery has been expected to be developed. As one means for reducing the manufacture cost, a method of continuously conducting unit operations such as film formation, printing and laser processing in an inline manner while rewinding a rolled-up flexible substrate around another roll is known. Such a method of continuously conveying a flexible substrate from one end to another is referred to as a Roll-to-Roll method. Particularly, the Roll-to-Roll method is generally used as means for continuously forming a semiconductor thin film such as a non-single crystalline silicon film on a flexible substrate (for example, a polymer film, a metal thin film and the like). The non-single crystalline silicon includes amorphous silicon, microcrystalline silicon and thin film polycrytalline silicon.
A Roll-to-Roll film formation apparatus is generally constituted to have a multi-chamber system including a plurality of film formation chambers in addition to a loading chamber and an unloading chamber. It is a long-shaped flexible substrate that is to be dealed in the Roll-to-Roll method film formation apparatus while being continuously conveyed. Accordingly, a gate valve for separating vacuum chambers from each other cannot be used. Therefore, if a film formation process is conducted in a film formation apparatus in which vacuum chambers are provided in a continuous manner, a gas degassed from a flexible substrate and a material gas used in each of the film formation chambers enter an adjacent film formation chamber to cause cross contamination, resulting in degradation of the quality of a semiconductor film.
A conventional method of preventing the cross contamination is disclosed in Japanese Patent Application Laid-Open No. Sho 59-34668. According to this method, a buffer chamber is provided between film formation chambers. An exhaust system, which is independent of each of the film formation chambers, is connected to the buffer chamber so as to obtain a higher degree of vacuum than that in the film formation chambers for controlling the ambience. FIG. 1 shows a conventional ambience separation method in which a buffer chamber is provided between film formation chambers. A buffer chamber 102 is provided between film formation chambers 101 and 103. Assuming that ambient pressures in the film formation chambers 101 and 103 are respectively Pc1 and Pc2 and an ambient pressure in the buffer chamber 102 is Pb1, the relationship: Pc1, Pc2 greater than Pb1 is established. It is desirable that a pressure in the buffer chamber 102 is one-tenth or less of that in the film formation chambers 101 and 103 upon film formation. The method described above prevents the cross contamination that a material gas for film formation introduced into each of the film formation chambers enters the adjacent film formation chamber. Although most of the material gas for film formation flowing into the buffer chamber is exhausted from the buffer chamber through an exhaust system of the buffer chamber, a means free path of gas molecules is long due to retention of a high vacuum, resulting in a problem that the ambience control is not sufficient in the buffer chamber by itself. Moreover, since a material gas for film formation flows from the film formation chamber containing a large amount of dust into the buffer chamber, this ambience separation method has such a structure that the dust is likely to be introduced along with the material gas flow. Accordingly, there arises another problem that dust more frequently adheres onto a substrate on which a film is to be formed, such as a flexible substrate.
Another method of preventing the cross contamination is disclosed in Japanese Patent Application Laid-Open No. Hei 9-107116. A connection tube (substantially, a buffer chamber) having an opening of the minimum cross-sectional size that allows a substrate for treatment to pass therethrough is provided between film formation chambers. An inert gas (hydrogen or rare gas) is introduced into the connection tube. FIG. 2 shows a conventional structure in which an inert gas is introduced through a connection tube that connects film formation chambers with each other for controlling the ambience. An inert gas 208 flows from a connection tube 204 into film formation chambers 201 and 203. Assuming that ambient pressures in the film formation chambers 201 and 203 are respectively Pc3 and Pc4 and an ambient pressure in the connection tube 204 is Ps1, the relationship: Ps1 greater than Pc3, Pc4 is established. According to this method, ambience control for each of the film formation chambers is effective. Moreover, the adherence of dust onto a substrate on which a film is formed is less. However, the inert gas mixes with a plasma for film formation to alter the quality of a semiconductor film. Although the inert gas is essentially inert, it acts as an impurity in the semiconductor film to alter physical properties such as electrically conductive properties.
In view of the above problems, the present invention has an object of conducting ambience separation between substrate treatment chambers in a substrate treatment apparatus including a plurality of substrate treatment chambers for continuously treating a substrate so as to prevent cross contamination, thereby preventing the degradation of the quality of a semiconductor film and the substrate treatment capacity due to enter of a gas different from the material gas into the substrate treatment chamber.
The present invention provides a substrate treatment apparatus including at least one treatment chamber and at least one buffer chamber having an exhaust system that is independent of the treatment chamber, wherein a connection tube is provided between the treatment chamber and the buffer chamber; and a gas inlet is provided for the connection tube. The connection tube has an opening of the minimum cross-sectional size that allows a substrate to be treated to pass therethrough.
FIG. 3 shows a structure for separation between substrate treatment chambers in one embodiment of the present invention. A buffer chamber 302 for ambience separation is provided between substrate treatment chambers 301 and 303. The substrate treatment chambers 301 and 303 and the buffer chamber 302 are connected to each other through connection tubes 304a and 304b respectively having inlet tubes 307a and 307b for a substrate treatment gas. The present invention is characterized in that the gas to be introduced through the connection tubes 304a and 304b is a gas for substrate treatment that is required in an adjacent substrate treatment chamber. For example, an introduced gas 308 is a gas used in the substrate treatment chamber 301, and an introduced gas 309 is a gas used in the substrate treatment chamber 303. The present invention makes it possible to treat a highly pure semiconductor film without altering an ambient composition in the substrate treatment chambers. Assuming that ambient pressures in the substrate treatment chambers 301 and 303 are respectively Pc5 and Pc6, ambient pressures in the connection tubes 304a and 304b are respectively Ps2 and Ps3, and an ambient pressure in the buffer chamber 302 is Pb2, the relationship: Ps2, Ps3 greater than Ps5, Ps6 greater than Pb2 is established. Based on this relationship of the pressure, the gas 308 for substrate treatment flows from the connection tube 304a into the substrate treatment chamber 301 and the buffer chamber 302, while the gas 309 for substrate treatment flows from the connection tube 304b into the substrate treatment chamber 303 and the buffer chamber 302. Therefore, the movement of dust from the substrate treatment chambers that contain a large amount of dust toward the buffer chamber never occurs against the gas flow. As a result, the adherence of dust onto the substrate to be treated becomes less.
The application of an ambience separation method of the present invention is not limited to a plasma treatment apparatus that is a plasma CVD apparatus, a sputtering apparatus, a plasma etching apparatus, or the combination of thereof. The ambience separation method of the present invention is also effective in a substrate treatment apparatus such as a thermal CVD apparatus and an evaporation apparatus in the case where ambience separation is required to be performed so as to continuously treat a substrate.